Set the potatoes in a medium pot and cover with cold water. Set over high heat and get the water boiling. Boil the potatoes until they are soft (about 15 minutes), then remove from heat and strain in a colander or sieve (save the cooked potatoes, throw away the water).
You'll need a large frying pan or skillet that has a cover, but we won't use the cover until later. Set the pan on the stove over high heat.
Add oil/butter, panch phoron, and bay leaf. Cook, stirring constantly, about 2-3 minutes until the spices begin to pop -- you will hear them clearly! Once they start popping, cook another 20-30 seconds.
Add the onion slices, and cook, stirring, until the onion is soft and translucent -- about 2-3 minutes.
Add the cauliflower, and cook, stirring, another 2 minutes. Add the turmeric and mix it in thoroughly.
Add the potatoes and cook over medium heat, stirring, for 2 minutes.
Add ½ cup water and reduce the heat to low. Now we cover the pan, and simmer for 5 minutes.
Check the tenderness of the cauliflower -- if it is not soft enough for you yet, add another ¼ cup water, cover, and simmer an additional 5 minutes and check again.
When finished, add salt and stir in before serving. Serve as a side dish, or as a main course over rice or grains.